Drilling fluid



3,537,992 DRILLING FLUID Jack H. Kolaian, Houston, Tex., assignor toTexaco Inc., New York, N.Y., a corporation of Delaware No Drawing. FiledApr. 25, 1967, Ser. No. 633,419 Int. Cl. Cm 3/14 US. Cl. 252--8.5 12Claims ABSTRACT OF THE DISCLOSURE An aqueous drilling fluid dispersantand a method of drilling wells using said drilling fluid which containsa substituted benzoic acid compound as the dispersant, namely,1,2,4-benzenetricarboxylic acid, the corresponding anhydride,1,2,4,5-benzenetetracarboxylic acid, 4-hydroxy 1,3 benzenedicarboxylicacid, 2,4-dihydroxybenzenecarboxylic acid, 2-hydroxy-4-ethoxy-benzenecarboxylic acid, and the corresponding alkalimetal including ammonium salts of these acids.

This invention relates to a novel aqueous drilling fluid for drillingwells through sub-surface formations by means of well drilling tools,and particularly to such an aqueous well drilling fluid having bothimproved dispersibility as a result of containing therein a noveldispersant as hereinafter more fully described. The invention is alsoconcerned with a method of drilling wells employing the novel aqueousdrilling fluid.

Drilling fluids, or muds as they are sometimes called, are slurries ofclayey solids used in the drilling of wells for tapping undergroundcollections of oil, gas, brine or water. Such fluids have a number ofdiflerent functions, the most important of which are to assist in theremoval of cuttings from the well, to seal off formations of gas, oil,or water which may be encountered at different levels, to lubricate thedrilling tool and drill pipe which carries the tool, and to hold thecuttings in suspension in event of shut-downs in drilling.

An ideal drilling fluid is a thixotropic colloidal system, i.e., a fluidwhich on agitation or circulation (as by pumping or otherwise), has ameasurable relatively low viscosity and is free flowing (not plastic),particularly at high temperatures; but when such agitation orcirculation is halted, the fluid sets or gels. The rate of gel formationis such as to permit the cuttings to fall only a short distance beforethe gel structure is sufiiciently strong to support them.

When such a drilling fluid having the proper viscosity, the proper gelrate and proper gel strength is circulated through a well bore, it has asufliciently high viscosity to carry the cuttings and sand from thebottom of the hole to the surface and it has a gel rate such as to allowthe cuttings and sand to settle in a settling pit. On standing in aquiescent state, it develops suflicient gel strength to prevent thesettling of the cuttings, sand or weighting material, etc., in the wellbore when it becomes necessary to discontinue circulation for anyappreciable period of time. Such a fluid is also characterized by itsability to form a mud cake on the borehole wall, thereby assisting insealing off the traversed formations and inhibiting socalled water loss,i.e., loss of water from the drilling fluid.

One of the principal problems in mud chemistry is the production ofsuitable drilling fluids having satisfactory dispersibility, and thenecessary thixotropic properties discussed above.

In accordance with the present invention the problems of dispersibilityin aqueous drilling fluids can be solved by incorporating in an aqueousdrilling fluid as the dispersant a substituted benzoic acid compoundselected nited States Patent 3,537,992 Patented Nov. 3, 1970 ice fromthe group consisting of (a) substituted benzoic acid compound having thegeneral formula (IJOOH (FOOH wherein D is hydrogen, hydroxy or ethoxyand wherein E is carboxy or hydrogen; and when D is hydrogen, E iscarboxy; and when D is hydroxy or ethoxy, E is hydrogen, saidsubstituted benzoic acid compound being present in the drilling fluid inan amount sufficient to reduce the viscosity thereto.

It is known from the article appearing in Zhur. Priklad. Khem. 35, pp.638-647 (1962), Organic Viscosity Reducer in Clay Solutions by D.Tischenko and S. Fleisher (CA, 57, 2491g, 1962), that theortho-dihydroxybenzenesulfonic acids, theortho-dihydroxy-alpha-toluenesulfonic acids and water soluble saltsthereof are viscosity reducing agents in clay laden drilling fluidswhereas the corresponding metaand para-dihydroxybenzenes including thecorresponding sulfonic acid derivatives and water soluble salts thereofare ineffective viscosity reducing agents for aqueous drilling fluids.

The term substituted benzoic acid compound as used in the specificationand claims is intended to cover any substituted benzoic acid compoundhaving the above general formulae and containing the prescribedsubstituents in the indicated locations on the benzene ring nucleus,including the alkali metal and ammonium salts of these benzoic acids.

More particularly, representative substituted benzoic acids of thepresent invention include l,2,4-benzenetricar'- boxylic acid anhydride,l,2,4-benzenetricarboxylic acid, 1,2,4,S-benzenetetracarboxylic acid,4-hydroxy 1,3 benzenedicarboxylic acid, 2,4 dihydroxybenzenecarboxylicacid and 2-hydroxy-4-ethoxybenzenecarboxylic acid.

It is surprising that these compounds are effective drilling fluiddispersants when other related benzoic acid compounds such as1,2-benzenedicarboxylic acid, 1,3-benzenedicarboxylic acid,1,4-benzenedicarboxylic acid, 1,3,5- benzenetricarboxylic acid and3-methoxy-4-hydroxy-benzaldehyde are ineffective dispersants in aqueousdrilling fluids.

The substituted benzoic acids of the present invention may be added toan aqueous drilling fluid in amounts ranging from about 01 pound toabout 10 pounds per barrel of drilling fluid. In general, it has beenfound that amounts less than 0.1 pound per barrel do not producecompletely satisfactory results in terms of dispersing activity whereasamounts above about 10 lbs. per barrel are economically unattractive andno improved results are obtained therewith. A preferred range for thesub- 3 stituted benzoic acids of the present invention is from about0.25 to about pounds per barrel of drilling fluid for most consistentresults and efficiency.

The substituted benzoic acids employed in the present invention areknown compounds and the manner of their preparation is known in the art.

In the tables, gel strength (Gels) is reported as determined by ashearometer in accordance with the procedure in the American PetroleumInstitute publication RP-29, results being expressed either aspounds/100 square feet or as time in seconds for a tube to settle in themud (after the mud has stood for zero time and for minutes). If itsettles in more than 60 seconds, shear is reported as pounds per hundredsquare feet. Yield Point (YP) is calculated by subtracting the PlasticViscosity (PV) from the Fann Viscosity reading at 300 rpm. PlasticViscosity 4 being expressed in Fann Viscosity at 600 r.p.m. and 300 rpm.for a direct reading viscosimeter.

The properties of the base muds are shown in the tables.

The test data set forth in the following tables indicate the surprisingadvantages of the substituted benzoic acids of the present invention anddemonstrate the beneficial results of same in improving thedispersibility of drilling fluids.

Representative physical properties of drilling fluids both before andafter addition of various materials including the substituted benzoidacids of the present invention are shown in the tables. In each examplethereof the amount of material or materials added to the base muds areshown, expressed in terms of pounds of material per barrel of drillingfluid.

TABLE I Shearomctcr gels, Amount lb./l00 an it. AII Type type AV, W.L.,Time, Example mud dispersant; PV Y1 cps. 10 pH cc hours 1 LpI-I 4A 8 9.42 8 9. 4 24 7 8. l 72 2 LpH 1 B 3 2 9. 7 0. 7 9. 3 2 14 8.8 24

2a LpH 4 l3 3 9. 8 0. 25 8 J. 4 2 8 t). 4 24 8 8. 5 28 7 8. l 72 3 LpI-I4 C 4 G 9.8 0. 25 7 t). G 2 S l. l 24 1 Lp =Low pH mud. 2 A1,2,4-benzenetricarboxylic acid anhydride. 3 B 1,2,4-benzenetricarboxylic acid. 4 C 1,2,4,5-b enzenetetracarboxylie acid.

(PV) is obtained by calculation, subtracting the Fann reading at 300r.p.m. from the 600 rpm. reading. Ap-

The data in Table I above show that 1,2,4-benzenetricarboxylic acid andits anhydride and 1,2,4,5-benzenetetraparent Viscosity (AV) is equal toone half of the Fann carboxylic acid of prescribed type are effective inreduc- Viscosity reading obtained at 600 rpm. The fluidity of a mud canbe back calculated from these data, the results ing the viscosity ofaqueous drilling fluids of the low pH type.

TABLE II Shearometer gels, Amount; 1b./l00 an it? API Type type AV,W.L., Time, Example mud dispersant PV YP cps. 0 10 pH cc. hours 4 LpH0.5D 2 9.8 0. 25 9. 7 2 9. 2 16 4a 4.0 D 9.1 O. 25 l. 0 2 9. 6 48 5 LpE0.5 E 3 9. 3 0. 25 10.0 2 9. 5 16 5a 2 0 E 7 6 9. 7 0. 25 U 9 10. 1 2 126 9. 8 16 c LpH 0.5 F 4 11 0. 25 17 2 19 16 6a LpH 2.0F 9 0,25 13 2 l9l6 2 D ,4-dihydroxybenzoic acid.

3 E= hydroxy-1,3-benzencdicarboxylic acid. 4 F=2-hydroxy-4-ethoxybenzoicacid.

The data in Table II above show that the materials used in Examples 4-6,inclusive, are capable of reducing the viscosities of low pH drillingfluids. The relatively low yield values and very low gel strength valuesshown for Example 4a are evidence of the good dispersing passed throughthe well in contact with earth formations during the drillingoperations, the improvement which comprises contacting said earthformations with an aqueous drilling fluid containing clay solidsdispersed therein and as the dispersant at least 0.1 pound per barrel ofeffect of 2,4-dihydroxybenzoic acid. Example 6a illusdrilling fluid of asubstituted benzoic acid compound trates that 2-hydroxy-4-ethoxybenzoicacid is effective at selected from the group consisting of4-hydroXy-1,3-bena concentration of 2.0 pounds per barrel.zenedicarboxylic acid, 2,4-dihydroxybenzenecarboxylic TABLE IIIShearometer gels, Amount 1b./l00 and 15. API Type type AV, W.L., Time,Example mud dispersant PV Y]? cps. 0 pH cc. hours 7 LpH 0.5 G 12 25 0.25 10 2o 2 15 23.5 5.2 15 9.4 14.7 15

7a LpH 2 G 5 59 0. 12 21 2 13 21 23.5 11 20 9.3 14.5 15

s LpH 2H 1 s3 0.25 9 55 2 8 54 33 50 9.2 15 15 9 LpH 41 7 47 0.25 5 25 25 19 14.5 7 5 8.7 9.8 25.9 24

10 LpH 415 5 3s 0.25 9 19 2 9 15 15.5 115 17 9.4 19.2 24

11 LpH 0.5 K 7 41 025 11 23 2 13 21 5 3 12 9.5 15 15 11a LpH 2K 5 250.25 10 23 2 11 20 9.5 15 9.4 15.8 15

l LpH=Low pH mud. Z G=1,3,5-benzenetricarboxylic acid. 3H=1,2-benzensdicarboxylic acid. 4 I=1,3-benzenedicarb oxylic acid. 5.T=1,4-benzenedicarboxylic acid. 5 K= -methoxy-4-hydroxybenzaldehyde.

The data in Table III above show that related comacid and2-l1ydroxy-4-ethoxybenzenecarboxylic acid, said pounds such as1,3,5-benzenetricarboxylic acid (Examples substituted benzoic acidcompound being present in the 7 and 7a) and the three isomers ofbenzenedicarboxylic drilling fluid in an amount sufficient to reduce theviscosacid (Examples 8, 9 and 10) are inefiective drilling fluid itythereof. dispersants in low pH mud systems. 45 8. A method as claimed inclaim 7 wherein the sub- Examples 11 and 11a show that3-methoxy-4-hydroxystituted benzoic acid is4-hydroxy-1,S-benzenedicarboxylic benzaldehyde is also an ineffectivedrilling fluid dispersacid. ant. 9. A method as claimed in claim 7wherein the subclaim; stituted benzoic acid is2,4-dihydroxybenzenecarboxylic 1. An aqueous drilling fluid containingclay solids disacldpersed therein and as the dispersant a substitutedbenzoic A method a filalmed 111 01mm 7 Wherem the acid compound Selectedf the group consisting f st tuted benzoic acid is2-hydroXy-4-ethoxybenzenecarboxhydroxy 1,3-benzenedicarboxylic acid,2,4-dihydroxy- Y acldbenzenecarboxylic acid and2-hydroxy-4-ethoxybenzene- A f clfilmed l 7 wherem the carboxylic acid,said substituted benzoic acid compound Stltuted benlolc acld 18 Presentn an amount of from being present in the drilling fluid in an amountsuflicient about to 10 P P F l 0f dfllllng fi to reduce the viscositythcreof 12. A method as claimed in claim 11 wherein the sub- An aqueousdrilling fl id as Claimed in claim 1 stituted bonzoic acid is present inan amount of from wherein the substituted benzoic acid is 4-hydroxy-1,3-about to 5 POunds P barrel of drlnlng fluldbenzenedicarboxylic acid. R fd 3. An aqueous drilling fluid as claimed in claim 1 e erences whereinthe substituted benzoic acid is 2,4-dihydroxy- UNITED STATES PATENTSbenzenecarboxylic acid.

4. An aqueous drilling fluid as claimed in claim 1 1999766 4/1935 Lawtonet a1 252 85 2,333,133 11/1943 Wayne 2528.5 wherein the substitutedbenzoic acid is 2-hydroxy-4- 2545169 3/1951 Salathiel 252 8 5ethoxybenzenecarboxylic acid.

5. An aqueous drilling fluid as claimed in claim 1 OTHER REFERENCESwherem the Substltuted benzolc acld 1S Present an Rogers, Compositionand Properties of Oil Well Drillg p from about to 10 pounds per barrelof 7 ing Fluids, 2nd edition, published 1953 by Gulf Pub. Co. dnllmgfluld- 0 of Houston, Texas-pp. 310, 319 to 322.

6. An aqueous dl'lllll'lg flu1d as claimed 1n cla1m 5 wherein thesubstituted benzoic acid is present in an H BER GUYNN, p i Examineramount of from about 0.25 to 5 pounds per barrel of drilling fluid. U.S.Cl. X.R.

7. A method of drilling wells wherein a drilling fluid is 252356

